A generic connecting system is known, for example, from U.S. Pat. No. 6,979,354, B2 and WO 2006/076011 A1.
In order to fasten a prosthesis, for example a lower leg prosthesis, to a residual limb in a reliable manner, a liner, which can consist, for example, of a silicone material, is first of all pulled over said residual limb. A connecting pin, which can be connected to the liner in various ways, is situated at the distal end of the liner.
A receiving device, which includes a receiving means into which said connecting pin is insertable, is situated, on the other hand, on the prosthesis shaft. To connect the prosthesis shaft to the liner, the connecting pin is simply inserted into the receiving means that is provided for this purpose. In this case, the pin comprises circumferential grooves by way of which it is able to engage in a pinion or toothed wheel which is situated in the receiving device. As a result of the particular development of said receiving device, the pin is only able to be inserted into the receiving means in this way without, however, being able to simply be pulled out of it again. A pressure mechanism, for example, by means of which the pinion or the toothed wheel is moved out of engagement with the grooves of the connecting pin, has to be actuated for this purpose.
A disadvantage is that the liner cannot be pulled over the residual limb in an identical manner every time by the patient such that the connecting pin which is situated on the liner is also arranged in slightly different orientations on the residual limb. As a result, it is possible for the connecting pin to be oriented wrongly for it to be able to be inserted into the receiving means of the prosthesis shaft.
Consequently, it is known from U.S. Pat. No. 6,589,288 B2 to provide the connecting pin on its end that faces the residual limb with a ball which interacts like a ball-and-socket joint with the fastening arrangement, by means of which the connecting pin is secured to the liner. As a result, it is possible to pivot and displace the connecting pin laterally within tight boundaries.
A disadvantage is that, in particular as a result of the lateral displaceability of the pin, only very small deviations from the optimum position of the connecting pin on the residual limb are able to be compensated. As a result of the pivotability, however, it is possible for the connecting pin to be able to be moved into the receiving means of the receiving device even when it is clearly situated away from its optimum position. When inserting the connecting pin into the receiving means, the connecting pin is consequently pivoted to the side such that the distal tip, that is the end of the connecting pin that is remote from the residual limb, projects into the receiving means. As a result of the connecting pin, in this case, however, having a clear angular deviation from its optimum position, it is possible that it cannot be inserted completely into the receiving means, which results in non-optimum fastening of the prosthesis shaft on the residual limb. Sore points and pain as well as wrong loads and wrong positions on the patient occur as a result.
In order to counter said problem, it is known from EP 1 435 880 B1 to develop the connecting pin in a totally flexible manner. It is formed, for example, from a synthetic material or as a helical spring and is realized so as to be flexible in every plane that coincides with its longitudinal axis and also so as to be elastically flexible in the axial direction. Consequently, a connecting pin of this type is able to compensate up to a certain degree for any wrong position and wrong positioning of the connecting pin relative to the receiving means of the receiving device. However, a disadvantage is that as a result of the flexibility and elasticity of the connecting pin which is necessary for this and is effective in all directions, the pressure stability thereof is clearly reduced. In particular when inserting the connecting pin into the receiving means of the receiving device when putting on the prosthesis system, the connecting pin can consequently buckle outward, instead of being inserted further into the receiving means. This results in the prosthesis shaft only being fastened to the liner in a very poor manner and additionally in wrong pressure loads and, where applicable, pressing points on the residual limb of the patient.